What happened
The pilot reported experiencing smoke originating from beneath the instrument panel while maintaining level flight at an altitude of 9,000 feet. This was immediately followed by a vibration lasting between 15 and 20 seconds. The pilot successfully diverted to Louisville, Kentucky, and landed without further incident.
The investigation
Post-accident examination revealed that the rudder and most of the vertical stabilizer had separated from the aircraft structure. Specifically, the rudder trim tab actuator arm had detached from the tab. Maintenance records indicated that work had been performed in the area of the rudder trim tab actuator arm attachment. A skin patch had been installed under the rudder trim tab bracket using four popped rivets, while eight rivets were used to attach the bracket to the trim tab.
Findings
The investigation determined that none of the 12 rivets met the standard for deforming or expanding to one and a half times their original diameter. This improper installation likely led to the structural failure. Additionally, an examination of the logbooks failed to reveal when the maintenance was performed.
improper rivet installation